Process of making cellulosic films



Sept. 20, 1932. J. B. WELLS ET AL 1,878,559

PROCESS OF MAKING CELLULOSIC FILMS Filed June 4, 1928 Jackson Wells Clarence L. A Wyzzci WWJZWM/ Patented Sept. 20, 1932 UNITED STATES,

PATENT OFFICE-1 zmoxson' B. WELLS Ann CLARENCE n. A. wYnn. or noonnsrnn, NEW YORK, AssIeNons T EASTMAN KODAK COMPANY, OF ROCHESTER,

NEW YORK PROCESS OF MAKING CELLUIAOSIG FILMS Application filed June 4, 1928. Serial No. 282,829.

This invention relates. to processes for the manufacture of films and similar products, especially processes in which the films are set in liquid baths instead of by evaporation.

When film is formed by this method, which has certain inherent advantages, it has been found that there is a tendency to the pro vent-s, more or less dissolved in the aqueous bath, differentially attack the film, thus giving the striated markings.

' The principal object of our invent-ion is to overcome this and otherdefects and to progigs a smooth highly polished surface on the Various types of scrapers, Squeegees, screens, sprays, etc, have been tried to overcome this inherent disadvantage in using the coagulation process and we have found that a submerged spray that immediately forces the difiiused solvents from the film zone produces a film that is highly polished and is. well suited tobe used as a photographic support. Other types of liquid agitating means may be used,-for example, small propellers or other mechanical impellers rotating beneath the surface of the liquid. Of course, when this result is obtained by liquid coagulation in other than non-aqueous liquids, our submerged spray will work as advantageously.

The above and other objects may be accomplished by the process herein described, which may be carried out in the apparatus about to be described. This apparatus, it is to be understood, is merely illustrative.

Reference will now be made to the accompanying drawing in the several figures of which the same reference characters denote the same parts, and in which NEW YORK, A CORPORATION OF 1 spraying device in a plane parallel to the axis of the drum; Fig. 3 is a diagram showing an alternative form of apparatus.

.Figs. 4: and 5 show details of a modification.

The viscous dope, after filtering, is poured into the elongated hopper 1. The lower part of this hopper is provided with accurately located. edge pieces 2 and 3. By turning the screw 4:, the. thickness of the film 5 coated on the, drum 8 from dope 6 in the hopper 1 may be controlled. Edge piece 2 pro jects slightly below edge piece 3, thus guiding a measured amount of dope 6 upon the drum 8, the outer surface of which is accurately polished. This cylinder rotates in a counterclockwise direction, the sheet of dope passes into the chamber 9 which contains the coagulating liquid 10, which is fed into the liquid reservoir from the intake 11, passes countercurrent to the film sheet and out the exit pipe 12. While inchambcr 9, the inequalities in the j film gradually disappear, due to the force of gravity, and the film acquires a uniform thickness. After it is submerged in the liquid a fine spray of the coagulating liquid is. forced against it from the spray pipes 13, which are'provided with numerous fine perforations or nozzles. The liquid from the bottom of the liquid res-ervoir is drawn through the pipe 14 and the filter 15 by means of the centrifugal pump 16 from which it is fed through the pipe 17 t0 the spray nozzles in the pipe 13. The arrows 13a. designate the fiow of liquid from the spray to the film surface. As the film progresses through a'bath, it gradually sets. It meets, as it advances, a coagulating liquid less concentrated in-the film solvents and when it hasv traversed approximately threequarters the circumference of the cylinder it is suificientlystrong to be removed therefrom over roller 18. 1

The formed film 20 may then pass through a suitable washing tank 30, and then through a drier 31. If desired,.thc air, rich in vaporized solvent from the drier, may pass through a scrubber 32 the water from'which is used to fill the tank 30. These elements are merely indicated diagrammatically in Fig. 1.

Between the point that the film leaves the roll and dope is applied, any suitable cleaning and polishing means for reconditioning the drum may be inserted, such as the apparatus shown conventionally and described in U. S. Patent No. 1,187,299, Reid, June 20, 1916. Apipe 19 is provided with fine perforations in its underside through which wacleaning liquid is not allowed to flow down the surface 7 to the stripped film 20, orthe bath 10, but is taken up by a dam in the shape of a hollow roll 21 having its periphery cov- .7

ered with a layer of soft rubber 22 through which a series of fine apertures are provided communicating to the center of the roll, the latter being connected to a vacuum apparatus, thus sucking the water through the'dam and out of the apparatus. The surface of the drum may be given a final conditioning by an absorbent roll 23, held against the surface by an adjustable spring 24.

Figure 2 illustrates one type of spray apparatus that may be used. The coagulating liquid is pumped into the spray at 19 and issued in a fine stream or spray from perforations or nozzles28 uniformly distributed along the horizontal pipes.

Figure 3 is a diagrammatic view of an alternate method of agitating the liquid below the surface of the bath 10 by means of the banks of propellers which are revolved by a gear train actuated-by the power driven shaft 26. i 7

It is preferable to have the spray totally submerged in order to keep the surface of the liquid bath quiet and free'from agitation, otherwise the film will have undesirable markings, caused by this surface action; The spray, on the other hand, should not be too far below the surface or much of its effectiveness is lost. We have found that the spray should cover approximately one-third of the area of the submerged film to insure optimum results. 7

It is desirable that thespray shall be as close to the surface as is possible without disturbance of the surface. The. actual distance will depend .onthe particular material treated, the speed of the drum, the force of the spray and the other variable factors. If the surface is agitated, there is a tendency for transverse markingsto appear, as dis tinguished from those. already 1 described which are more or less longitudinal of the film. v

One way to insure that the layer'entering the bath will be free from disturbing surface irregularities ofthe bath is by providing a roller 35, as shown in Figure 4, which is spaced slightly from the layer 5'and is driven as indicated by the arrow, so'that its surface near the film moves in adirection Jopposite to the movement of the film, thus sup porting a constant bead of liquid at 27.

In a modification shown in Figure 5, a roller 36 rests with slight pressure against thelayer 5 at the point where it enters the bath 10 and is driven by its'contact with the layer. It tendsto smooth out irregularities -.in the surface of the layer. ter issprayed upon the surface 7. This pipe is parallel to the axis of the drum 8. 7 The lVe have further discovered that, in gen- :eral, both kinds of markings are less if the air in chamber 9 is warmed and circulated gently throughmeans of pipes 29, the action being apparently that there is a slight skinning over of-the film surface prior to its reaching the setting bath proper.

This heated chamber is, therefore, useful in itself whether or not the submerged agitation is carried out.

Any suitable type of cellulosic dope or coagulating bath may be employed, such as are known in connection with the coagulation of viscose and cellulosic esters. As atypical example, may be mentioned nitrocellulose in a solution of methyl and butyl alcohol coagulated in an aqueous bath, such as described in the copending application of J ackson B. Wells, Serial No. 253,361, filed February 10, 1928. The apparatus herein described, except as otherwise specified, is of the type shown in said application, or it may be of the type shown in Reid Patent No. 1,187,929,June 20,1916. 7 e

It is to be understood, however, that this process is general in its application to the formation of films, threads and the like, and is not confined to the specific materials and structure mentioned. YVe consider as withinour invention all such modifications and equivalents as'fall within the scope of the appended claim.

Having thus described our invention what we claim as new, and desire to secure by Letters Patent is,*

In the process ofmaking smooth flexible films bythe method in which a coagulable layer of cellulosic material is spread on a continuously moving smooth support, passed through a setting bath, and then stripped from said support inthe" form of a continuous band, andthen passed through an aqueous bath anda drier in turn, the steps of recovering from the air of the drier vaporized solvents by means of a water scrubber and utilizing the water from the scrubber for the aqueous'bath.

Signed at Rochester, New York, this 24th day of May, 1928. r

1 JACKSON B. WELLS.

CLARENOE L. A. 'WYND. 

